You could try creating a set links (in the related-link element) with role="child". That will pull in the title and shortdesc of the target chapters. If your target chapters only have an abstract element, and no shortdesc, you could consider adding the shortdesc within the abstract to identify the bits you want pulled into the overview/used generally as link previews.

For HTML output, you could manage the link creation via the map, but that probably won't work in PDF (depending on what PDF output process you're using). So links with role="child" could be the safest bet.

Alternatively, you could reuse bits of the abstract directly into the overview topic, by targetting the elements inside of the chapter abstracts. For example, you can't pull an <abstract> into body content, but you can pull <p> or <ul> elements, which are both allowed inside <abstract>s.

Hope this helps - if it doesn't, consider asking on the dita-users mailing list. (Check its archives for similar answers first). 

 Michael Priestley